1. Field of the Invention
The present invention is generally related to a method for controlling a fuel system of a marine propulsion engine and, more particularly, to a method for controlling a canister purge valve in order to manage the fuel vapor associated with a fuel supply module.
2. Description of the Related Art
Many different types of fuel handling systems associated with marine propulsion systems are well known to those skilled in the art. Fuel vapor separators and other types of fuel system modules are used to segregate fuel vapor from liquid fuel and to direct the fuel vapor away from fuel pumps whose operation can be adversely affected by the presence of vapor within the fuel supply.
U.S. Pat. No. 3,835,822, which issued to Mickle et al. on Sep. 17, 1974, discloses a cooled fuel pump for internal combustion engines. The pump includes a cast aluminum housing. A water cooling tube is embedded in the housing and connected directly to the inlet of the main cooling system of the engine such that upon initial starting of the engine, cooling water is immediately supplied to the fuel pump to reduce its temperature, and thereby eliminate vapor lock conditions.
U.S. Pat. No. 4,844,043, which issued to Keller on Jul. 4, 1989, discloses an anti-vapor lock carbureted fuel system. A marine fuel system includes a first crankcase pressure driven fuel pump supplying fuel from a remote fuel tank to a vapor separator, and a second crankcase pressure driven fuel pump supplying vapor-free fuel from the vapor separator to the carburetors of the engine. In combination, a squeeze bulb and one-way check valve supply fuel from the remote fuel tank directly to the carburetors for starting the engine.
U.S. Pat. No. 5,103,793, which issued to Riese et al. on Apr. 14, 1992, discloses a vapor separator for an internal combustion engine. The assembly includes a bowl member and a cover member. A fuel pump is located in the internal cavity of the bowl member and has its inlet located in the lower portion of the bowl member cavity, for supplying fuel thereto. The fuel pump is secured in position within the bowl member by engagement of the cover member with a fuel pump. The cover member includes a mounting portion for mounting a water separating filter element to the vapor separator assembly. The cover member includes structure for routing fuel from the discharge of the water separating filter element to the interior of the bowl member internal cavity.
U.S. Pat. No. 5,389,245, which issued to Jaeger et al. on Feb. 14, 1995, discloses a vapor separating unit for a fuel system. The unit includes a closed tank having a fuel inlet through which fuel is fed to the tank by a diaphragm pump. The liquid level in the tank is controlled by a float-operated valve. An electric pump is located within the vapor separating tank and has an inlet disposed in the tank and an outlet connected to a fuel rail assembly of the engine. Excess fuel from the fuel rail assembly is conducted back to the upper end of the vapor separator tank. A vapor venting mechanism is incorporated in the tank to vent vapor from the tank.
U.S. Pat. No. 6,253,742, which issued to Wickman et al. on Jul. 3, 2001, discloses a fuel supply method for a marine propulsion engine. The method uses a lift pump to transfer fuel from a remote tank to a vapor separator tank. Only one level sensor is provided in the vapor separator tank and an engine control unit monitors the total fuel usage subsequent to the most recent filling of the tank. When the fuel usage indicates that the fuel level of the vapor separator tank has reached a predefined lower level, a lift pump is activated to draw fuel from a remote tank and provide that fuel to the vapor separator tank.
U.S. Pat. No. 6,553,974, which issued to Wickman et al. on Apr. 29, 2003, discloses an engine fuel system with a fuel vapor separator and a fuel vapor vent canister. The system provides an additional fuel chamber, associated with a fuel vapor separator, that receives fuel vapor from a vent of the fuel vapor separator. In order to prevent the flow of liquid fuel into and out of the additional fuel chamber, a valve is provided which is able to block the vent of the additional chamber. In addition, a sensor is provided to provide a signal that represents a condition in which liquid fuel within the additional fuel chamber exceeds a predetermined level.
U.S. Pat. No. 6,694,955, which issued to Griffiths et al. on Feb. 24, 2004, discloses a marine engine with primary and secondary fuel reservoirs. The system comprises first and second fuel reservoirs connected in fluid communication with each other. The first fuel reservoir is a fuel vapor separator which has a vent conduit connected in fluid communication with a second fuel reservoir. Under normal conditions, fuel vapor flows from the fuel vapor separator and into the second fuel reservoir for eventual discharge to the atmosphere. Any liquid fuel caused to flow out of the vent conduit of the fuel vapor separator is contained within the second fuel reservoir and prevented from being discharged into the cavity under the cowl of an outboard motor and eventually into a body of water in which the marine system is operated.
U.S. Pat. No. 6,718,953, which issued to Torgerud on Apr. 13, 2004, discloses a fuel vapor separator with flow directing components within a fuel recirculating flow path. A fuel delivery system for a marine engine provides first, second, and third reservoirs of a fuel vapor separator and first, second, and third pumps to cause fuel to be drawn from the fuel tank and provided to the combustion chambers of an internal combustion engine. A flow directing component is provided to inhibit recirculated fuel from mixing directly with fuel within the fuel vapor separator that has not yet been pumped to a fuel rail. The flow directing component receives recirculated fuel and also receives fuel from a second reservoir through an orifice formed through a surface of the flow directing component.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
It would be significantly beneficial if a fuel system of a marine propulsion engine could control the pressure within a fuel reservoir, such as a fuel vapor separator or fuel system module, in such a way that both a lift pump and a high pressure pump within the fuel vapor separator can work properly with the pressure within the fuel system module.